During setup, you will be asked to install the mailvelope browser extension. Mailvelope specialized in end-to-end encryption and has partnered with GMX to ensure the integrity of encrypted communication. GMX guarantees that the software is trustworthy. Mailvelope will carry out any tasks that need to take place locally on your device (as opposed to on a GMX server) including:
Why? True end-to-end encryption only works, if the process actually takes place on your computer and not inside of the infrastructure of GMX.
The mailvelope-websites have a characteristic background made up of different shapes and icons, which you can customize in the mailvelope settings. In the rare event of coming across a fake mailvelope website, this feature can help you identify and distinguish the fake website from the real one. Visit mailvelope.com/help for a more detailed documentation.
The binaries provided by GMX are signed and can be checked for integrity by any PGP tool. Please find our code signing key at https://img.ui-portal.de/hilfe/codesigning.mailvelope.com.pub.asc. Its fingerprint is 16F4 5CCC 1848 12B4 AC93 0EF3 60DD 1F16 B339 0CD1.
Confused? You don't need to understand this section to use mailvelope. The point is that any software developer can verify whether mailvelope works as described and doesn't include backdoors or other entry points.